When should packed red blood cells (pRBCs) be administered after a postpartum hemorrhage (PPH)?

When to Administer pRBCs After Postpartum Hemorrhage

Packed red blood cells (pRBCs) should be administered when hemoglobin levels fall below 70 g/L (7 g/dL) or when there is ongoing hemorrhage with hemodynamic instability in patients with postpartum hemorrhage (PPH). 1

Transfusion Thresholds Based on Clinical Guidelines

Hemoglobin-Based Criteria

• Primary threshold: Hemoglobin < 70 g/L (7 g/dL) in stable patients 1
• Secondary threshold: Hemoglobin < 90 g/L (9 g/dL) in unstable patients or those with active bleeding 1
• For patients with cardiovascular disease or brain injury, consider a more liberal transfusion threshold (80-90 g/L) 1

Clinical Assessment Criteria

Blood transfusion decisions should not be based solely on hemoglobin levels but should incorporate:

1. Patient physiology:

   • Hemodynamic instability (tachycardia, hypotension)
   • Signs of inadequate tissue perfusion
   • Decreased urine output
   • Altered mental status

2. Blood loss estimation:

   • Severe PPH defined as > 500 mL after vaginal delivery or > 1000 mL after cesarean section 1
   • Consider transfusion when blood loss exceeds 1.5 L or approximately 25% of blood volume 2

3. Response to initial resuscitation:

   • Persistent tachycardia or hypotension despite fluid resuscitation
   • Worsening acidosis or increased lactate levels

Transfusion Strategy for PPH

Initial Management

1. Directly measure blood loss by weighing soaked pads and linen 1
2. Draw blood for complete blood count, coagulation studies, and crossmatch
3. Consider point-of-care hemoglobin testing and viscoelastic testing if available 1
4. Administer tranexamic acid 1 g IV within 3 hours of birth 1

Transfusion Algorithm

1. For hemoglobin < 70 g/L: Transfuse pRBCs regardless of clinical status 1
2. For hemoglobin 70-90 g/L:
   • If hemodynamically stable without active bleeding: Monitor without transfusion
   • If unstable or active bleeding: Transfuse pRBCs 1
3. For massive hemorrhage (continued bleeding after initial measures):
   • Implement balanced transfusion with 1:1:1 ratio of pRBCs:FFP:platelets 1, 2
   • Monitor coagulation parameters and fibrinogen levels

Special Considerations

Fibrinogen Levels

• Normal fibrinogen in pregnancy: 4-6 g/L
• Hypofibrinogenemia (< 2 g/L) with ongoing bleeding predicts progression to severe PPH 1
• Consider fibrinogen replacement with cryoprecipitate or fibrinogen concentrate when levels fall below 2 g/L 1

Transfusion Ratios

• For massive PPH requiring multiple units, a balanced transfusion approach with ratios of 1:1:1 to 1:2:4 (pRBCs:FFP:platelets) is recommended 1
• Higher FFP:RBC ratios (closer to 1:1) have been associated with reduced need for additional interventional procedures 3

Monitoring During Transfusion

• Continuous assessment of vital signs
• Serial hemoglobin measurements
• Coagulation parameters (PT/INR, aPTT, fibrinogen)
• Urine output
• Clinical signs of ongoing bleeding

Common Pitfalls to Avoid

1. Delayed recognition of significant blood loss: Visually estimated blood loss often underestimates actual loss by 30-50%

2. Over-reliance on hemoglobin levels: Initial hemoglobin may not reflect acute blood loss; clinical assessment is crucial

3. Delayed transfusion: Don't wait for laboratory confirmation in cases of obvious severe hemorrhage with hemodynamic instability

4. Under-correction of coagulopathy: Monitor and correct fibrinogen levels, which drop early in obstetric hemorrhage

5. Failure to administer tranexamic acid: Should be given within 3 hours of birth for all cases of PPH 1

By following these evidence-based guidelines for pRBC transfusion in PPH, clinicians can optimize maternal outcomes while avoiding unnecessary transfusions and their associated risks.